The present invention relates to cooling a thermal head of a thermal image recording apparatus, and more particularly to a structure that allows the prevention of rising temperatures within the image recording apparatus.
FIG. 3 is a perspective view showing the main portion of a conventional device for cooling a thermal head disclosed, e.g., in Japanese Patent Application (UPA) No. 147374/1985 (the term "UPA" as used herein means "Unexamined Published Application").
In the figure, reference numeral (1) designates a thermal head; (2), a radiating fin mounted on the thermal head (1); (3), a platen roller; (4), a sheet of image recording paper; (5), a blower; (6) a conduit for guiding a stream of air from the blower (5); and (7), a slot, arranged on the conduit (6), through which the stream of air exists.
The operation of the conventional device for cooling a thermal head as constructed above will be described. In a thermal image recording apparatus, a predetermined image is recorded on the image recording sheet (4) by heat generated by an electric signal applied to heating elements of the thermal head (1). The amount of picture element formation on image sheet depends on such factors as the temperature of the heating elements, i.e., the amount of electric energy applied to the heating elements and the temperature of the thermal head (1) itself. The electric energy applied to the heating elements is controlled within a prescribed range by a control circuit. The thermal head (1), on the other hand, keeps the temperature from rising by dissipating the heat accumulated through printing from the radiating fin (2). Also, the stream of air produced by the blower (5) is directed to the radiating fin (2) from the slot (7) to improve the radiating efficiency of the radiating fin (2) and to make the temperature distribution of the thermal head (1) uniform. Generally, the conventional device for cooling the thermal head is accommodated within a case that constitutes the image recording apparatus.
With the device for cooling a thermal head constructed as described above, the air blown from the blower (5) to the radiating fin (2) and thus heated by going through the radiating fin (2) circulates within the case of the image recording apparatus, thereby increasing the temperature inside the image recording apparatus as a whole. Hence, the thermal head (1) is also heated, and as a result, there is caused a problem in that the increase in temperature within the image recording apparatus reduces the life of various parts, especially, of electric components, constituting the image recording apparatus.